Cathode uniformity is a critical factor for commercializing field emission displays (FEDs). Carbon nanotube (CNT) materials have the highest potential as cathode materials for future FEDs. Uniformly and selectively depositing CNTs over a large substrate is one of the main issues for an FED fabrication process. A typical means of growing carbon nanotubes on a substrate is to use chemical vapor deposition (CVD) techniques with catalyst activation. This technique requires a relatively high growth temperature, thereby increasing the production cost. It is also difficult to achieve a film with uniform properties over a large area. Other methods, such as screen-printing or dispensing, have been developed to deposit CNTs in paste or ink composites. The composites consist of CNT powder mixed with conductive or non-conductive particles, carriers or vehicles and binders in some cases. The size and shape of the patterns created by these techniques are often non-uniform from spot to spot resulting in a non-uniform effective emitting area for each pixel or subpixel. Furthermore, edge emission from the printed or dispensed CNT composite ink or paste commonly results in non-uniformity performance of the CNT cathode, making the cathode fabrication process unpredictable.
For FED applications, depositing the same amount of CNTs on each pixel or sub-pixel with uniform effective emitting area is a major goal for obtaining uniform emission current from an individual pixel or sub-pixel. On the other hand, ideally, CNT deposition is the last step in the cathode fabrication procedure, especially for triode structures. Once a CNT cathode is prepared, further wet chemical process or etching processes that may degrade the cathode performance should not be applied to the surface of the CNT cathode.